My GSD is now 14 months and she has always chased the cats. It is play time in her mind. She leaves them when I tell her leave it with no problems. She can be chewing on a bone and the cat can walk up to her, rub up against her, and share that bone. I'm positive that if the cat took her bone she would not react by growling or biting. She would watch the cat, follow the cat, talk to the cat, then if all of that fails she will come to me and tell on the cat. In saying that I try to keep them separated, so that they can each eat in peace. But I know that if by accident one approaches the other, there will be no problems. The puppy needs to be taught that its not good to react that way. You don't want the puppy to react that way either. Not to you, other people, other dogs, or cats.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD